1. Field of the Invention
This invention relates to gas turbine engine thrust reversers, and more particularly to cascadeless, translating cowl thrust reversers for ducted fan gas turbine engines, which redirect the air flow in the duct outwardly and forwardly when the thrust reverser is deployed.
2. Background Information
One general type of thrust reverser for use with the air duct of a turbofan engine incorporates a translating cowl that forms a rearward, outer wall portion of the air duct. For normal rearward air flow through the air duct, the translating cowl resides in a closed position in which its forward end engages a bulkhead that is mounted on the fan cowl of the engine. To reverse the air flow, the translating cowl is moved in an aft direction away from the bulkhead leaving an outlet opening aft of the bulkhead through which air is discharged from the air duct. The thrust reverser also provides for blocking of the air duct at a location aft of the outlet opening.
In one form of blocking system, a number of blocking doors are pivotally mounted on the translating cowl and coupled by linkages to the engine cowl. When the translating cowl moves rearwardly upon deployment of the thrust reverser, the linkages pivot the blocking doors radially inwardly to positions in which they block the air duct. Another form of blocking system is an inner wall member on the translating cowl that is located and shaped to form the outer wall of the portion of the duct inwardly of the thrust reverser outlet opening when the translating cowl is in the forward position and to block the air duct when the translating cowl is in the rearward, reverse-thrust position.
Cascade thrust reversers, as are known in the art, provide a cascade of flow turning vanes to assist in turning the flow therethrough to provide the forward component of velocity. U.S. Pat. No. 4,232,516 describes a cascadeless thrust reverser which deflects the air flow through an aperture in a forward direction. An annular plate is positioned on the fan cowl and projects into the turbulent flow region in the air duct. The annular plate and the side wall define a recess open to the flow which delays the separation of the flow from the side wall. U.S. Pat. No. 6,029,439 describes a pivot-door thrust reverser having a plurality of pivoting doors. At least one guide vane is connected to the fan cowl bulkhead and located within the air duct when a thrust reverser door is in the forward thrust position so as to guide the air passing through the reverse thrust opening.
A disadvantage of the prior art cascadeless thrust reversers is that they provide no method or structure for controlling the plume which is directed forwardly when the thrust reverser is deployed. Such plumes may impinge upon the fuselage and aircraft control surfaces and thereby affect the stability of the aircraft during landing and may cause foreign object damage to the engine rotating machinery.
Accordingly, there is a need in the art for a cascadeless translating cowl thrust reverser which provides sufficient reverse thrust with minimal effect on the stability of the aircraft and minimal effect on the engine operation when the thrust reverser is deployed.